f89bb68fe2
When we enable CDC on a table, Scylla creates a log table for it.
It has default properties, but the user may change them later on.
Furthermore, it's possible to detach that log table by simply
disabling CDC on the base table:
```cql
/* Create a table with CDC enabled. The log table is created. */
CREATE TABLE ks.t (pk int PRIMARY KEY) WITH cdc = {'enabled': true};
/* Detach the log table. */
ALTER TABLE ks.t WITH cdc = {'enabled': false};
/* Modify a property of the log table. */
ALTER TABLE ks.t_scylla_cdc_log WITH bloom_filter_fp_chance = 0.13;
```
The log table can also be reattached by enabling CDC on the base table
again:
```cql
/* Reattach the log table */
ALTER TABLE ks.t WITH cdc = {'enabled': true};
```
However, because the process of reattachment goes through the same
code that created it in the first place, the properties of the log
table are rolled back to their default values. This may be confusing
to the user and, if unnoticed, also have other consequences, e.g.
affecting performance.
To prevent that, we ensure that the properties are preserved.
A reproducer test,
`test_log_table_preserves_properties_after_reattachment`, has been
provided to verify that the changes are correct.
Another test, `test_log_table_preserves_id_after_reattachment`, has
also been added because the current implementation sets properties
and the ID separately.
Fixes scylladb/scylladb#25523
Backport: not necessary. Although the behavior may be unexpected,
it's not a bug per se.
Closes scylladb/scylladb#26443
* github.com:scylladb/scylladb:
cdc: Preserve properties when reattaching log table
cdc: Extract creating columns in CDC log table to dedicated function
cdc: Extract default properties of CDC log tables to dedicated function
schema/schema_builder.hh: Add set_properties
schema: Add getter for schema::user_properties
schema: Remove underscores in fields of schema::user_properties
schema: Extract user properties out of raw_schema
Scylla
What is Scylla?
Scylla is the real-time big data database that is API-compatible with Apache Cassandra and Amazon DynamoDB. Scylla embraces a shared-nothing approach that increases throughput and storage capacity to realize order-of-magnitude performance improvements and reduce hardware costs.
For more information, please see the ScyllaDB web site.
Build Prerequisites
Scylla is fairly fussy about its build environment, requiring very recent versions of the C++23 compiler and of many libraries to build. The document HACKING.md includes detailed information on building and developing Scylla, but to get Scylla building quickly on (almost) any build machine, Scylla offers a frozen toolchain. This is a pre-configured Docker image which includes recent versions of all the required compilers, libraries and build tools. Using the frozen toolchain allows you to avoid changing anything in your build machine to meet Scylla's requirements - you just need to meet the frozen toolchain's prerequisites (mostly, Docker or Podman being available).
Building Scylla
Building Scylla with the frozen toolchain dbuild is as easy as:
$ git submodule update --init --force --recursive
$ ./tools/toolchain/dbuild ./configure.py
$ ./tools/toolchain/dbuild ninja build/release/scylla
For further information, please see:
- Developer documentation for more information on building Scylla.
- Build documentation on how to build Scylla binaries, tests, and packages.
- Docker image build documentation for information on how to build Docker images.
Running Scylla
To start Scylla server, run:
$ ./tools/toolchain/dbuild ./build/release/scylla --workdir tmp --smp 1 --developer-mode 1
This will start a Scylla node with one CPU core allocated to it and data files stored in the tmp directory.
The --developer-mode is needed to disable the various checks Scylla performs at startup to ensure the machine is configured for maximum performance (not relevant on development workstations).
Please note that you need to run Scylla with dbuild if you built it with the frozen toolchain.
For more run options, run:
$ ./tools/toolchain/dbuild ./build/release/scylla --help
Testing
See test.py manual.
Scylla APIs and compatibility
By default, Scylla is compatible with Apache Cassandra and its API - CQL. There is also support for the API of Amazon DynamoDB™, which needs to be enabled and configured in order to be used. For more information on how to enable the DynamoDB™ API in Scylla, and the current compatibility of this feature as well as Scylla-specific extensions, see Alternator and Getting started with Alternator.
Documentation
Documentation can be found here. Seastar documentation can be found here. User documentation can be found here.
Training
Training material and online courses can be found at Scylla University. The courses are free, self-paced and include hands-on examples. They cover a variety of topics including Scylla data modeling, administration, architecture, basic NoSQL concepts, using drivers for application development, Scylla setup, failover, compactions, multi-datacenters and how Scylla integrates with third-party applications.
Contributing to Scylla
If you want to report a bug or submit a pull request or a patch, please read the contribution guidelines.
If you are a developer working on Scylla, please read the developer guidelines.
Contact
- The community forum and Slack channel are for users to discuss configuration, management, and operations of ScyllaDB.
- The developers mailing list is for developers and people interested in following the development of ScyllaDB to discuss technical topics.